From Amy Fobes at Battelle (comments are hers from the original recipe card)

Dressing: 1 C vinegar
3/4 C sugar (amazing, huh?)
1/4 C salad oil (I use vegetable oil)
1 tsp celery seed
1 tsp salt
1/4 tsp pepper

This is enough marinade for a small salad — I frequently double it.

Use whatever kinds of veggies you want, cook if necessary & marinate 6 8 hours, stirring every few hours.

Recommended vegetables include: zucchini, broccoli, red and green peppers, cherry tomatoes, onions, olives you name it!